The Third Revolution in "Ligand Field” Theory - the Ionization Energy of the Partly Filled Shell is Sometimes Larger than of the Ligand Orbitals

Abstract

In several d-group and in most 4f group compounds, the ionization energy of the partly filled shell has been shown by photoelectron spectrometry to be higher than of the loosest bound filled molecular orbitals. This has the unexpected consequence that the anti-bonding M. O. has higher ionization energy than the corresponding bonding M. 0. of the same symmetry type, and invites thinking about what are sub-shell energy differences in “ligand field” theory.